Before we jump into the Human Microbiome Project, let's review what these scientists are studying. Microbe is one of those words that we hear and blithely skip over, thinking it's just a catchall for something small and vaguely bacterial. Which, it turns out, is kind of accurate.

While bacteria certainly comprise a large part of our microbiome, some other lesser-known microbes make up our microbial party, too. Take archaea, which are so similar to bacteria that, for a long time, scientists just assumed they were bacteria. Not so. They actually have different amino acids and sugars and a different genetic structure. Once thought to reside only in extreme environments, archaea have been found in the oral, intestinal and vaginal mucous membranes of humans.

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Then you have protozoa, which we sometimes call "germs" because some types can cause dysentery or malaria, but they're a little bigger than bacteria. And let's not forget the fungus among us, which can cover skin without much consequence -- or move into infection territory. Viruses also are part of our microbiome, but don't think they're just idly waiting on dirty hands to give you a cold.

In fact, our microbes largely aren't lazy houseguests hitching a ride on our body. They could be more aptly compared to the well-managed staff of a fabulous estate. For instance, one of the more important functions of viruses in the microbiome is to infect bacteria, changing either how the bacteria work or how much there is. So it's useful to think of viruses as working with (or against) bacterial function in our body [source: Williams].

When suffering from a cold and railing against germs, remember that without microbes you couldn't eat or breathe. While not on the body, photosynthetic bacteria in water produce half our oxygen [source: University of Utah]. Microbes pack our system to aid digestion and synthesize vitamins, and you might be excited to report at your next dinner party that half your stool is not leftover food but microbial biomass that is quickly replenished in your gut [source: Kolata]. The good ones fend off the infection or illness-causing microbes and strengthen our immune system, and -- as we're learning courtesy of the Human Microbiome Project -- do a heck of a lot more.